Hi John, Suggestions
Try another distributor cap
Do a compression test hot on 1 and 2
I cooked a similar engines exhaust valves on 1 & 2 when crud blocked the
front carb needle valve and leaned the front pair out.
Would start and run for 5 miles before losing all power.
Peter
----- Original Message -----
From: "John Slade" <edalsj@igs.net>
To: "List, Alpine" <alpines@autox.team.net>
Sent: Sunday, September 01, 2002 10:59 AM
Subject: 1725 Engine problems
> I have run into an engine problem that I can't diagnose, and am
> wondering if any out there have had a similar experience.
>
> Situation....freshly restored car with essentially a brand new engine.
> New 1725 factory short block, which I have been carrying around with me
> for the last 25 years, fitted with all overhauled/reconditioned
> accessories. Head and cam overhauled by a reputable machine shop, engine
> built up by me (I've done several before), distributor and Stromberg
> carbs overhauled by me, etc, etc. New spark plugs, clean fuel lines with
> an in line filter. Various vacuum hoses checked and found leak free.
> Points and spark plugs correctly set, as were the tappets.
>
> Engine initially started, and distributor set to approx 70 BTDC. Carb
> mixtures adjusted to give reasonable running. Car idled at about 1200
> rpm. Drove car for about 2 miles at modest rpms, then shut down.
>
> Next day, started car OK, went for a drive, and after about 2 miles,
> engine started to miss, and get a little rough. Got worse as I returned
> home. Found that I could remove number 1 and number 2 spark plug wires
> with no change to engine running, though still with a big spark on the
> leads. Fiddling with throttle and choke had no positive effect. Both
> carbs seemed to be working, i.e. as I blipped the throttle, both pistons
> raised a little.
>
> Let engine cool down, then attempted to restart. Started fine, ran
> smoothly for about two minutes, or until things started to get warm.
> Then the misfiring returned, same symptoms...nothing from #1 and #2
cylinders.
>
> Let the engine cool down, and repeated. Same results as before...ran
> fine for a couple of minutes or so, then went off.
>
> I assumed that the front carb was acting up, so removed the carbs, and
> replaced the front one with another which had not been overhauled, but
> which had worked successfully on a 1725 a couple of years before.
> Replaced the carbs, and started the engine....exactly the same symptoms.
> While fiddling around in this condition, I blocked off the air intake to
> the front carb with a leather work glove....the engine smoothed out
> noticeably (perhaps not completely), but at a lower rpm than when the
> engine was started.
>
> At this point I am a bit stumped. Perhaps I have some sort of vacuum/air
> leak which only occurs as the engine warms up, perhaps there is
> something I haven't thought about. If it is a leak, how come it only
> affects the front two cylinders? The problem does not appear to be
> electrical, since there continues to be good sparking at the front two
> cylinders. Since I replaced the front carb with another, it seems not to
> be directly front carb related.
>
> Any comments and/or advice will be appreciated. I'd like to get this
> sorted so that I can go driving this weekend!
>
> John Slade
> Manotick, ON
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